A spark ignition safety circuit and starting circuit having grounding of the primary winding through safety switches and preferably also through the ignition switch. The primary winding of the ignition circuit is grounded through closed safety switches which are in series with the ignition switch.
This invention relates to an ignition circuit and starting circuit for an internal combustion engine on a small motor vehicle such as a lawn mower and more particularly to a spark ignition circuit and starting circuit which is grounded through closed safety switches to improve safety and reliability of operation.
Small gasoline engines have been operated with ignition systems and distributors on multicylinder engines. Safety switches with interlocks are used to insure safety in operation and generally operate in some manner to prevent the engine from starting or to shut off the engine if a dangerous situation exists. Stopping the engine manually may be accomplished simply by pressing a grounding conductor against a spark plug which shorts out the ignition and causes the engine to stop.
A more sophisticated arrangement has been developed using a module consisting of solid state circuitry to control operation of the engine and for stopping the engine when desired. This arrangement using the module of solid state circuitry for stopping the engine has become unnecessarily complicated and requiring unnecessarily expensive components in the circuitry, and in some cases not entirely reliable.
Accordingly, the applicant has provided for a safety switch in the low voltage high current portion of the ignition circuit Essentially this operates to ground the primary coil of a magneto or a capacitor discharge spark ignition system. Preferably, one or more safety switches are connected through the ignition switch to operate the ignition system or to shut off the internal combustion engine by opening one or more of the safety switches or the ignition switch. Safety switches are also used in the starting circuit as well to prevent injury to the operator when the engine starts. The safety switch may relate to such switches as used in the transmission, more commonly known as the neutral safety switch which prevents starting of the engine if the transmission is in gear. Similarly, a power take-off safety switch is also provided when the power take-off shaft is engaged through the driving clutch which thereby would produce a live power take-off shaft if the engine should start. These switches have been used in the prior art internal combustion engines, but are not used in this manner and accordingly it is believed that the use of the safety switches and ignition switch as used in the applicant's invention provides for greater safety and improve reliability.